Leanstack was on Bootstrap 2. Chose this because it is wildly popular, so it’s active, has been used a lot in production, and has a ton of features. Anything you need to do from a UI perspective, there’s likely a plugin for it already part of the library. Haven’t tried the others, but we're happy with BS.

For StackShare, we upgraded to Bootstrap 3. I don’t like that they changed the name of columns, essentially breaking the grid layout for Bootstrap 2 and below, so that was a real pain to update. I hope they don’t do that again. Once we have more bandwidth, we’re totally going to decouple our markup from Bootstrap.

Building responsive front-end User Interfaces, forms, menus, buttons, dropdowns, etc in a predictable uniform way is the key to users understanding what you want them to do on your web based application.

I wrapped several Bootstrap components with ReactJS (i.e. turned them into ReactJS components), and used them in the app's UI. Also, I used numerous Bootstrap CSS classes in building the app's custom components, along with several Bootstrap plugins.

We started with a bootstrap based template and then completely rewrote it due to poor design of the template. Using boostrap properly was a great experience - once you learn it and use it properly, it's simple to use and very good at being responsive and adapting to the various screen view.

With the advancement in CSS, Bootstrap is creating new milestones when it comes to minimising our CSS codes. So elegant and beautiful yet easy and convenient to use once you go through all the classes and its elements. In addition, its JS function is impressive too.

Bootstrap is a framework to help you design websites faster and easier. It includes HTML and CSS based design templates for typography, forms, buttons, tables, navigation, modals, image carousels, etc. It also gives you support for JavaScript plugins.
Bootstrap's responsive CSS adjusts to phones, tablets, and desktops
Bootstrap is compatible with all modern browsers (Chrome, Firefox, Internet Explorer, Safari, and Opera)

In process of Learning Technics.
stable and responsive frameworks .A novice developer like me with just some basic knowledge of HTML and little CSS can easily get started with Bootstrap.open source projects.